The present invention relates to a backwash alluvial filter with a plurality of filter elements, as well as to its utilization for washing out solid matter.
Filters for fluids are known, comprising filtering elements which are composed of suspended candles and removable in rows. One of such filters are disclosed, for example, in the German Offenlegungsschrift No. 2,741,639. This filter has a filter container with a collecting pipe located in the interior of the container and mounting a plurality of suspended filter elements arranged one behind the other. The collecting pipes are located adjacent to one another on supporting bodies and can be removed from the filter container by rows.
The Austrian Pat. No. 211,329 shows a device for backwashing of filter candles arranged in rows and mounted on the collecting conduit in standing position. The collecting conduits extend at both sides horizontally through the container wall. The arrangement at both sides is very expensive. In addition, each collecting conduit is provided with two locking elements for the plurality of tank openings and require a plurality of valves and armatures.
In all methods and arrangements the outlet valves for the clarified filtrate must be switched to backwash mode during the backwashing. This means that a clarified filtrate cannot be recovered during the entire backwashing operation.